In a printing press, the rollers are each carried on at least one support that is movable linearly on a respective guide.
In printing with such a printing press ink is typically transferred from a print roller onto a substrate or web gripped between the print roller and a counter-pressure roller. Flexographic printing is basically performed by three rollers. An anilox roller transfers ink to a printing roller whose textured surface holds the ink and prints the ink onto a substrate sandwiched between the print roller and a counter-pressure roller. Flexographic printing can be performed with a wide range of water- or oil-base inks, and prints well on a variety of different substrate materials like plastic, foil, acetate film, paper, tissue, and other similar materials.
Adjustment of the rollers is important for the operation of a printing press. Typically two adjustment modes are used:
1. Coarse adjustment in which the rollers are moved at high speed in order to achieve a fast clearance that could be used for a change of formats on the printing roller or for maintenance.
2. Fine adjustment of the rollers necessary for precise movement in order to optimize the printing quality for example with a different substrate.
U.S. Pat. No. 3,604,350 provides a solution for a coarse and fine adjustment of a roller of a flexographic printing press where the coarse adjustment is effected by a pair of gears mounted on a transverse movable gear shaft. For coarse adjustment, the shaft is moved into a position where the gears engage a rack on a support of a roller, in this position rotation of the shaft imparts fast movement to the roller. For fine adjustment, the shaft is moved into a position where the gears are not engaged with the rack and movement of the rollers is only performed by spindles extending parallel to the movement direction of the roller.
Another solution for a combination of coarse and fine adjustment is published in the German application DE 102 42 009. It describes a printer with spindles that are parallel to the movement direction of the roller and engageable with gears mounted on motor-driven shafts. For coarse adjustment the shaft is moved into a position in which the gears are engaged with the spindles and automatic rotation of the motor driven shaft provides fast movement of the roller. Fine adjustment is performed by manual rotation of the spindles with the shaft positioned such that the gears are disengaged from the spindles.
Disadvantages of the existing solutions for coarse adjustment are additional drives or actuators, force transfer, bearing, and coupling elements. In addition, no sufficient precise predetermining of individual formats and no simultaneous automatic and manual operation are possible. The required space and the construction costs of the known solutions for additional coarse adjustment are also very substantial. The necessary special adaptation to circumstances, in other words the lack of universality, is another shortcoming of the known solutions.